This patent is directed to a method and system for generating a source of electron donors for use in denitrification, and, in particular, to a method and system using pulsed electric fields to release intracellular materials from biological materials for use in denitrification.
Wastewater flowing into a conventional wastewater treatment plant may have a high level of nitrogen compounds (such as nitrates, nitrites, etc.) relative to that which is desirable in the water exiting the plant. These nitrogen compounds may be the product of commercial activity, for example. Alternatively, the nitrogen compounds may be the product of agricultural activity, including runoff from fields fertilized using ammonium nitrates.
One way to lower the level of nitrogen compounds is to pass the treated water through an anoxic reactor to conduct a process known as denitrification. However, the anoxic reactor will require a supply of electron donors and possibly a source of carbon to permit the necessary reactions to occur. Many conventional wastewater treatment plants use compounds such as methanol, ethanol or glycol as the supply of the electron donor and carbon.
The use of compounds such as methanol or ethanol is not without its disadvantages. For one thing, methanol and ethanol are flammable substances that require great care in usage, transport and storage. Additionally, while the amount of methanol or ethanol used on a daily basis may not be that large (relative to the amount of water that is treated), the amounts used over a longer period of time may be quite substantial. Given the price of these substances, and the volatility of the price, this can be a considerable budgetary concern for wastewater plant operators, on the order of $250,000 per year for a plant treating ten million gallons of wastewater per day.
Consideration has been given to using waste organic and cellular material as an electron donor. However, the kinetics of cell oxidation of waste organic and cellular material is so slow as to prevent waste organic and cellular material from being considered as a viable alternative to conventional electron donors, such as methanol or ethanol.